Effective tissue displacement with elastic impression materials can be accomplished by
1. injection of the material into the gingival sulcus.
2. placement of chemical-impregnated cords into the gingival sulcus.
3. electrosurgical means.
4. a firm tray material.

All of the above

(1) (2) (3)

(1) and (3)

(2) and (4)

(4) only